Detecting Direct Collapse Black Holes: making the case for CR7

TL;DR

This paper presents evidence that the CR7 system at redshift 6.6 may host the first direct collapse black hole, formed around redshift 20, based on spectral analysis and cosmic evolution modeling.

Contribution

It proposes a novel interpretation of CR7 as a direct collapse black hole candidate supported by spectral fitting and cosmic history analysis.

Findings

CR7's spectrum fits nebular emission from a primordial gas around a black hole.

A DCBH could have formed at redshift ~20 in the CR7 host halo.

CR7 may be the first candidate of a direct collapse black hole.

Abstract

We propose that one of the sources in the recently detected system CR7 by Sobral et al. (2015) through spectro-photometric measurements at $z = 6.6$ harbors a direct collapse blackhole (DCBH). We argue that the LW radiation field required for direct collapse in source A is provided by sources B and C. By tracing the LW production history and star formation rate over cosmic time for the halo hosting CR7 in a $\Lambda$CDM universe, we demonstrate that a DCBH could have formed at $z\sim 20$. The spectrum of source A is well fit by nebular emission from primordial gas around a BH with MBH $\sim 4.4 \times 10^6 \ \rm M_{\odot}$ accreting at a 40 % of the Eddington rate, which strongly supports our interpretation of the data. Combining these lines of evidence, we argue that CR7 might well be the first DCBH candidate.